Epoxy resins have been widely used in the fields of electronics and coatings with high levels of functionality because epoxy resins have a low shrinking property at the time of curing and cured articles thereof are excellent in dimensional stability, electrical insulating properties and chemical resistance. However, for example, since there has been required reflow resistance and so on accompanied with transition to surface mounting of a semiconductor, miniaturization of semiconductor itself or a lead-free solder in the field of electronics such as a semiconductor encapsulating material and so on, much more heat impact resistance has been required for electronic element materials, and thus there has been demanded a material of a low melt viscosity in which fillers can be highly filled.
As an epoxy resin having low viscosity satisfying such required properties, for example, there have been known epoxy resin compositions based on a diglycidylether of dihydroxy tri(phenylene ether) (refer to Reference 1 described below).
However, recently in the field of coatings with a high level of functionality, since it has been inevitable to response to environmental problems represented by a dioxin problem and there have been highly demanded a so-called halogen-free flame-retardant system in which a resin itself has a flame retarding effect without using a halogen-type flame retardant in additives, the above-described epoxy resins having tri(phenylene ether) as a main skeleton are not sufficient in a flame retarding effect of cured articles thereof and thus have not manifested a halogen-free flame retarding effect. Further, the above-epoxy resins are insufficient in strength of the resin structure itself and thus inferior in heat resistance of cured articles thereof.
Therefore, there has been a situation in that epoxy resins excellent in fluidity of the resins themselves as well as in flame retardancy and heat resistance of cured articles thereof were not obtained.
Patent Document 1: Japanese Patent Application Laying-Open Publication No. Hei 05-304001.